Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H,W=map(int,input().split())
maze=[]
white=0
for i in range(H):
    s=input()
    c=s.count(".")
    white+=c
    maze.append(s)
path=[[None]*W for _ in range(H)]
path[0][0]=1
q=deque([[0,0]])
while q:
    h,w=q.popleft()
    for nh,nw in ([h+1,w],[h-1,w],[h,w+1],[h,w-1]):
        if nh<0 or nh>H-1 or nw<0 or nw>W-1:
            continue
        if maze[nh][nw]=="#" or path[nh][nw]!=None:
            continue
        q.append([nh,nw])
        path[nh][nw]=path[h][w]+1
        if nh==H-1 and nw==W-1:
            print(white-path[nh][nw])
            exit()
print(-1)